Meconium Aspiration Syndrome

Written by Darla Burke | Published on August 15, 2012
Medically Reviewed by George Krucik, MD

What is a Meconium Aspiration?

Meconium is dark-green fecal material that is produced in the intestines of a fetus before birth. After delivery, your newborn expels meconium stools for the first few days of life. Stress your baby experiences before or during birth may cause expulsion of meconium into the amniotic fluid (fluid that surrounds the fetus).

Stress can also cause your baby to gasp inside your uterus and inhale, or aspirate, amniotic fluid into his or her lungs. If meconium is present in the amniotic fluid, this is known as meconium aspiration or meconium aspiration syndrome (MAS). Your newborn can also breathe in amniotic fluid containing meconium shortly after birth.

Although MAS is often not life threatening, it can cause significant health complications for your newborn.

What Causes Meconium Aspiration Syndrome?

MAS occurs when your baby experiences stress. Stress often results when the amount of oxygen available to the fetus is reduced. Causes of this may include:

  • a pregnancy that goes past the due date (more than 40 weeks)
  • difficult or long labor
  • certain health issues experienced by the mother, including hypertension (high blood pressure) or diabetes

Pregnancy that lasts more than 40 weeks can result in “aging” of the placenta. The placenta is the organ that provides nourishment to the fetus in the womb. When the placent ages, it is not able deliver enough oxygen to the fetus. As a result, MAS is more common in postmature (overdue) newborns, compared with premature newborns.

What Are the Symptoms of MAS?

The most prominent symptom of MAS is respiratory distress. Your infant may breathe rapidly or grunt during breathing. Some newborns may stop breathing if their airways are blocked by meconium. Your baby may also exhibit the following MAS symptoms:

  • cyanosis (bluish skin color)
  • limpness
  • low blood pressure

How Is Meconium Aspiration Syndrome Diagnosed?

A diagnosis of MAS is made based on your newborn’s symptoms and the presence of meconium in the amniotic fluid.

Your doctor will listen to your infant’s chest with a stethoscope to detect abnormal breath sounds. Tests used to confirm the diagnosis may include:

  • blood gas test to evaluate oxygen and carbon dioxide levels
  • chest X-ray to see if material has entered your newborn’s lungs

How Is Meconium Aspiration Syndrome Treated?

If MAS occurs, your newborn will need immediate treatment to remove the meconium from the lungs. After delivery, a tube will be placed in your newborn’s windpipe to suction the fluid containing meconium from the lungs. The suctioning will continue until no meconium is seen in the material removed.

If your newborn is not breathing or has a low heart rate, your doctor will place a mask over the newborn’s face. This will deliver oxygen to your baby and help inflate his or her lungs.

After emergency treatment has been provided, your newborn may be placed in a special-care unit to observe his or her breathing. Additional treatment may be needed to avoid complications of MAS. These treatments include:

  • antibiotics, such as ampicillin and gentamicin to prevent or treat an infection caused by the meconium
  • the use of a ventilator (breathing machine) to help your infant breathe
  • extracorporeal membrane oxygenation (ECMO) if your baby also has persistent high blood pressure. For this treatment, a pump and artificial lung do the work of your newborn’s heart and lungs so that these organs can heal.
  • oxygen therapy to make sure there is enough in the blood
  • the use of a radiant warmer to help your baby maintain body temperature

What Complications Are Associated With Meconium Aspiration?

Most newborns with MAS will not have any long-term health complications. However, MAS is a serious issue that can have an immediate impact on your newborn’s health. Meconium in the lungs can cause inflammation and infection. It can also block the airways. This can cause lung overexpansion. If a lung inflates too much, it can rupture or collapse. Then air from inside the lung can accumulate in the chest cavity and around the lung. This condition, known as a pneumothorax, makes it difficult to reinflate the lung.

MAS increases the risk of your infant developing persistent pulmonary hypertension of the newborn (PPHN). High blood pressure in the vessels of the lungs restricts blood flow and makes it difficult for your baby to breathe properly. PPHN is a rare, but life-threatening condition.

Severe MAS may limit oxygen to the brain. This can cause permanent brain damage. However, this complication is rare.

What Is the Outlook for Newborns with Meconium Aspiration?

Infants who experience mild complications of MAS usually recover well. Infants who develop brain damage or PPHN as a result of MAS may face lifelong health issues that require medical support.

How Can Meconium Aspiration Be Prevented?

Prevention of MAS requires the early detection of risk factors. Fetal monitoring before delivery is needed to determine whether your baby is experiencing stress. Your doctor can take steps to alleviate fetal distress during labor and reduce the potential for MAS to develop.

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